Hundreds of workers were told to go into a “take cover” position after the tunnel in a plutonium uranium extraction (PUREX) plant collapsed.

The agency says the rail tunnels are hundreds of feet long, with about eight feet (2.4 meters) of soil covering them. The U.S. Department of Energy says the incident caused the soil above the tunnel to sink between 2 and 4 feet (half to 1.2 meters).

“I would underscore this is confined to a small area of the Hanford site,” Destry Henderson, deputy news manager for the Hanford Joint Information Center, told NBC News. “The facility does have radiological contamination right now but there is no indication of a radiological release,” Henderson said.

A manager sent a message to all personnel telling them to “secure ventilation in your building” and “refrain from eating or drinking.”

A source said “take cover” status was expanded to the entire site at 10:35 a.m. The source also said that crews doing road work nearby may have created enough vibration to cause the collapse, and that Vit Plant employees were in cover mode as well.